System and method for positioning an elongate member with respect to an anatomical structure

ABSTRACT

Methods and apparatus for an ablation device used in the treatment of atrial fibrillation comprise an elongate shaft and a positioning mechanism adjacent the distal end of the shaft. The positioning mechanism is adapted to facilitate location of an anatomic structure and also to anchor the elongate shaft adjacent the anatomic structure. The positioning mechanism comprises an electrode for stimulating the anatomic structure as well as sensing electrical signals. Also, an energy delivery element is adjacent the distal end of the shaft and is adapted to stimulate the anatomic structure and create a zone of ablation that blocks abnormal electrical activity thereby reducing or eliminating atrial fibrillation in the patient.

CROSS-REFERENCE

This application is a continuation of U.S. patent application No.12/480,929 (Attorney Docket No. 31760-704.201, formerly 027680-000210US)now U.S. Pat. No. ______ filed Jun. 9, 2009, which is a non-provisionalof, and claims priority to U.S. Provisional Application No. 61/061,362(Attorney Docket No. 31760-704.101, formerly 027680-000200US) filed Jun.13, 2008, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to medical devices and methods,and more specifically to improved devices and methods for positioning anablation device in a human or animal patient. The device may be used totreat atrial fibrillation.

The condition of atrial fibrillation is characterized by the abnormal(usually very rapid) beating of left atrium of the heart which is out ofsynch with the normal synchronous movement (“normal sinus rhythm”) ofthe heart muscle. In normal sinus rhythm, the electrical impulsesoriginate in the sino-atrial node (“SA node”) which resides in the rightatrium. The abnormal beating of the atrial heart muscle is known asfibrillation and is caused by electrical impulses originating instead inthe pulmonary veins (“PV”) [Haissaguerre, M. et al., SpontaneousInitiation of Atrial Fibrillation by Ectopic Beats Originating in thePulmonary Veins, New England J Med., Vol. 339:659-666].

There are pharmacological treatments for this condition with varyingdegrees of success. In addition, there are surgical interventions aimedat removing the aberrant electrical pathways from PV to the left atrium(“LA”) such as the Cox-Maze III Procedure [J. L. Cox et al., Thedevelopment of the Maze procedure for the treatment of atrialfibrillation, Seminars in Thoracic & Cardiovascular Surgery, 2000; 12:2-14; J. L. Cox et al., Electrophysiologic basis, surgical development,and clinical results of the maze procedure for atrial flutter and atrialfibrillation, Advances in Cardiac Surgery, 1995; 6: 1-67; and J. L. Coxet al., Modification of the maze procedure for atrial flutter and atrialfibrillation. II, Surgical technique of the maze III procedure, Journalof Thoracic & Cardiovascular Surgery, 1995; 2110:485-95]. This procedureis shown to be 99% effective [J. L. Cox, N. Ad, T. Palazzo, et al.Current status of the Maze procedure for the treatment of atrialfibrillation, Seminars in Thoracic & Cardiovascular Surgery, 2000; 12:15-19] but requires special surgical skills and is time consuming.

There has been considerable effort to copy the Cox-Maze procedure for aless invasive percutaneous catheter-based approach. Less invasivetreatments have been developed which involve use of some form of energyto ablate (or kill) the tissue surrounding the aberrant focal pointwhere the abnormal signals originate in PV. The most common methodologyis the use of radio-frequency (“RF”) electrical energy to heat themuscle tissue and thereby ablate it. The aberrant electrical impulsesare then prevented from traveling from PV to the atrium (achievingconduction block within the heart tissue) and thus avoiding thefibrillation of the atrial muscle. Other energy sources, such asmicrowave, laser, and ultrasound have been utilized to achieve theconduction block. In addition, techniques such as cryoablation,administration of ethanol, and the like have also been used.

There has been considerable effort in developing the catheter basedsystems for the treatment of AF using radiofrequency (RF) energy. Onesuch method is described in U.S. Pat. No. 6,064,902 to Haissaguerre etal. In this approach, a catheter is made of distal and proximalelectrodes at the tip. The catheter can be bent in a J shape andpositioned inside a pulmonary vein. The tissue of the inner wall of thePV is ablated in an attempt to kill the source of the aberrant heartactivity. Other RF based catheters are described in U.S. Pat. Nos.6,814,733 to Schwartz et al., 6,996,908 to Maguire et al., 6,955,173 toLesh; and 6,949,097 to Stewart et al.

Another source used in ablation is microwave energy. One such device isdescribed by Dr. Mark Levinson [(Endocardial Microwave Ablation: A NewSurgical Approach for Atrial Fibrillation; The Heart Surgery Forum,2006] and Maessen et al. [Beating heart surgical treatment of atrialfibrillation with microwave ablation. Ann Thorac Surg 74: 1160-8,2002].This intraoperative device consists of a probe with a malleable antennawhich has the ability to ablate the atrial tissue. Other microwave basedcatheters are described in U.S. Pat. Nos. 4,641,649 to Walinsky;5,246,438 to Langberg; 5,405,346 to Grundy, et al.; and 5,314,466 toStem, et al.

Another catheter based method utilizes the cryogenic technique where thetissue of the atrium is frozen below a temperature of −60 degrees C.This results in killing of the tissue in the vicinity of the PV therebyeliminating the pathway for the aberrant signals causing the AF [A. M.Gillinov, E. H. Blackstone and P. M. McCarthy, Atrial fibrillation:current surgical options and their assessment, Annals of ThoracicSurgery 2002; 74:2210-7]. Cryo-based techniques have been a part of thepartial Maze procedures [Sueda T., Nagata H., Orihashi K., et al.,Efficacy of a simple left atrial procedure for chronic atrialfibrillation in mitral valve operations, Ann Thorac Surg 1997;63:1070-1075; and Sueda T., Nagata H., Shikata H., et al.; Simple leftatrial procedure for chronic atrial fibrillation associated with mitralvalve disease, Ann Thorac Surg 1996; 62: 1796-1800]. More recently, Dr.Cox and his group [Nathan H., Eliakim M., The junction between the leftatrium and the pulmonary veins, An anatomic study of human hearts,Circulation 1966; 34:412-422, and Cox J. L., Schuessler R. B., BoineauJ. P., The development of the Maze procedure for the treatment of atrialfibrillation, Semin Thorac Cardiovasc Surg 2000; 12:2-14] have usedcryoprobes (cryo-Maze) to duplicate the essentials of the Cox-Maze IIIprocedure. Other cryo-based devices are described in U.S. Pat. Nos.6,929,639 and 6,666,858 to Lafintaine and 6,161,543 to Cox et al.

More recent approaches for the AF treatment involve the use ofultrasound energy. The target tissue of the region surrounding thepulmonary vein is heated with ultrasound energy emitted by one or moreultrasound transducers. One such approach is described by Lesh et al. inU.S. Pat. No. 6,502,576. Here the catheter distal tip portion isequipped with a balloon which contains an ultrasound element. Theballoon serves as an anchoring means to secure the tip of the catheterin the pulmonary vein. The balloon portion of the catheter is positionedin the selected pulmonary vein and the balloon is inflated with a fluidwhich is transparent to ultrasound energy. The transducer emits theultrasound energy which travels to the target tissue in or near thepulmonary vein and ablates it. The intended therapy is to destroy theelectrical conduction path around a pulmonary vein and thereby restorethe normal sinus rhythm. The therapy involves the creation of amultiplicity of lesions around individual pulmonary veins as required.The inventors describe various configurations for the energy emitter andthe anchoring mechanisms.

Yet another catheter device using ultrasound energy is described byGentry et al. [Integrated Catheter for 3-D Intracardiac Echocardiographyand Ultrasound Ablation, IEEE Transactions on Ultrasonics,Ferroelectrics, and Frequency Control, Vol. 51, No.7, pp 799-807]. Herethe catheter tip is made of an array of ultrasound elements in a gridpattern for the purpose of creating a three dimensional image of thetarget tissue. An ablating ultrasound transducer is provided which is inthe shape of a ring which encircles the imaging grid. The ablatingtransducer emits a ring of ultrasound energy at 10 MHz frequency. In aseparate publication [Medical Device Link, Medical Device and DiagnosticIndustry, February 2006], in the description of the device, the authorsassert that the pulmonary veins can be imaged.

While these devices and methods are promising, improved devices andmethods for positioning a device relative to an anatomic structure suchas the pulmonary vein are needed. Furthermore, it would also bedesirable if such devices could create single or multiple ablation zonesto block abnormal electrical activity in the heart in order to lessen orprevent atrial fibrillation. Such devices and methods should be easy touse, cost effective and simple to manufacture.

Description of Background Art

Other devices based on ultrasound energy to create circumferentiallesions are described in U.S. Pat. Nos. 6,997,925; 6,966,908; 6,964,660;6,954,977; 6,953,460; 6,652,515; 6,547,788; and 6,514,249 to Maguire etal.; 6,955,173; 6,052,576; 6,305,378; 6,164,283; and 6,012,457 to Lesh;6,872,205; 6,416,511; 6,254,599; 6,245,064; and 6,024,740; to Lesh etal.; 6,383,151; 6,117,101; and WO 99/02096 to Diederich et al.;6,635,054 to Fjield et al.; 6,780,183 to Jimenez et al.; 6,605,084 toAcker et al.; 5,295,484 to Marcus et al.; and WO 2005/117734 to Wong etal.

In all above approaches, the inventions involve the ablation of tissueinside a pulmonary vein or at the location of the ostium. The anchoringmechanisms engage the inside lumen of the target pulmonary vein. In allthese approaches, the anchor is placed inside one vein, and the ablationis done one vein at a time.

SUMMARY OF THE INVENTION

The present invention generally relates to medical devices and methodsand more particularly relates to devices and methods for positioning anablation device used in the treatment of atrial fibrillation.

In a first aspect of the present invention, an ablation device fortreating atrial fibrillation in a patient comprises an elongate shafthaving a proximal end and a distal end. A positioning mechanism isadjacent the distal end of the shaft and is adapted to facilitatelocation of an anatomic structure and also adapted to anchor theelongate shaft adjacent the anatomic structure. The positioningmechanism comprises an electrode for stimulating the anatomic structureand also for sensing electrical signals from the anatomic structure. Anenergy delivery element is adjacent the distal end of the shaft and isadapted to stimulate the anatomic structure and create a zone ofablation that blocks abnormal electrical activity thereby reducing oreliminating atrial fibrillation in the patient.

The elongate shaft may comprise a lumen extending between the proximaland ends of the shaft. The shaft may be rotatable around the positioningmechanism. The shaft may also have a sidewall with a windowtherethrough, and the energy delivery element may be adapted tostimulate the anatomic structure through the window.

The positioning mechanism may be slidably disposed in the lumen, and itmay be in a substantially linear configuration while disposed in thelumen. The positioning mechanism may exit the shaft via an aperture in asidewall of the shaft. The positioning mechanism may comprises a coil ora plurality of wires expandable from a contracted configuration to anexpanded configuration. In the expanded configuration, the plurality ofwires may form a cage-like structure. The plurality of wires may also bebiased to flare radially outward when unconstrained. The positioningmechanism may be adapted to exert an outward biasing force against aninterior surface of the anatomical structure thereby anchoring theelongate shaft thereto. The anatomic structure may be a pulmonary veinand the positioning mechanism may be adapted to indicate an angle ofentry of the elongate shaft into the pulmonary vein. In still otherembodiments, the positioning mechanism may comprise a proximal wire anda distal wire, both proximal and distal wires at least partiallyencircling the elongate shaft.

The electrode may operate in a monopolar mode or the electrode maycomprise a plurality of electrodes operating in a bipolar mode.

The energy delivery element may comprise an ultrasound transducer. Theenergy delivery element may also be adapted to deliver radiofrequencyenergy, microwaves, light energy, thermal energy, or cryogenic coolingto the anatomic structure. The zone of ablation may be a linear region,an annular region, or an arcuate. The zone of ablation may encircle oneor more than one pulmonary veins or the zone of ablation may be outsideof and adjacent a pulmonary vein. The energy delivery element often mayremain unobstructed by the positioning mechanism.

In another aspect of the present invention, a method of ablating ananatomic structure in a patient as a treatment for atrial fibrillationcomprises providing an elongate shaft having a proximal end and a distalend and locating the anatomic structure with a positioning mechanismdisposed adjacent the distal end of the shaft. The shaft is anchoredadjacent the anatomic structure with the positioning mechanism and anelectrode adjacent a distal portion of the positioning mechanism is usedto electrically stimulate or sense electrical signals from the anatomicstructure. Energy is delivered to the anatomic structure with an energydelivery element near the distal end of the shaft, thereby creating azone of ablation that blocks abnormal electrical activity in order toreduce or eliminate atrial fibrillation in the patient.

The elongate shaft may comprise a lumen extending between the proximaland distal ends and the method may further comprise delivering a fluidfrom the lumen to the anatomic structure. The step of locating theanatomic structure may comprise visualizing the anatomic structure, ortactile or audible feedback. The positioning mechanism may be advancedfrom or retracted into the elongate shaft during the step of locating.The positioning mechanism may comprise a plurality of wires and theanatomic structure may be located by deflecting at least some of theplurality of wires. Locating the anatomic structure may also comprisedetermining an entry angle of the elongate shaft into the anatomicstructure.

The step of anchoring the shaft may comprise engaging the positioningmechanism against the anatomical structure and exerting an outwardbiasing force against an interior surface of the anatomical structure.Anchoring may also comprise forming and engaging a cage-like structureon the positioning mechanism with the anatomic structure.

The step of stimulating the anatomic structure may comprise stimulatingin a monopolar or bipolar mode. Stimulating may also comprise pacing thepatient's heart. The stimulating step may be performed before, during orafter creation of the ablation zone.

Delivering energy to the anatomic structure may comprise delivering oneof ultrasound energy, radiofrequency energy, microwave, light, andthermal energy. The step of creating the zone of ablation may comprisecreating a linear or arcuate ablation path such as when the zone ofablation encircles one or more than one pulmonary vein. Sometimes theelongate shaft may be rotated around the positioning mechanism whiledelivering energy. The energy may be delivered through a window in theelongate shaft and the energy may be directed at an angle between 65 and115 degrees to the anatomic structure. Delivering energy may compriseadjusting power, frequency, bandwidth, or amplitude of the energydelivered to the anatomic structure. The method may further comprisecooling the anatomic structure with cooling fluid.

These and other embodiments are described in further detail in thefollowing description related to the appended drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are drawings of the system of the preferred embodimentof the invention;

FIGS. 2-4 are drawings of three rotation variations of the system of thepreferred embodiment of the invention;

FIGS. 5-8C are drawings of a first variation of the positioningmechanism of the system of the preferred embodiment of the invention;

FIGS. 9A and 9B are drawings of a second variation of the positioningmechanism of the system of the preferred embodiment of the invention;

FIGS. 10A and 10B are drawings of a third variation of the positioningmechanism of the system of the preferred embodiment of the invention;

FIG. 11 is a drawing of a fourth variation of the positioning mechanismof the system of the preferred embodiment of the invention; and

FIG. 12 is a drawing of a fifth variation of the positioning mechanismof the system of the preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description of preferred embodiments of the invention isnot intended to limit the invention to these embodiments, but rather toenable any person skilled in the art to make and use this invention.

As shown in FIGS. 1A and 2, the system 10 of the preferred embodimentsincludes an elongate member 12 and a positioning mechanism 14 coupled tothe elongate member 12. The elongate member 12 may be radiopaque toallow it to be seen during fluoroscopy. This may be achieved withradiopaque marker bands or by including radiopaque filler materials inthe elongate member such as barium sulfate or titanium dioxide. Thepositioning mechanism 14 performs one or more of the followingfunctions: (a) facilitate locating an anatomical structure (preferably apulmonary vein 3000 in a left atrium of a heart 3002, but alternativelyany other suitable anatomical structure), (b) anchor the elongate member12 with respect to the anatomical structure, and (c) electricallystimulate and/or sense electrical signals from the anatomical structure.The system 10 is preferably designed for positioning an elongate memberwithin a patient and, more specifically, for positioning a therapyand/or navigation catheter with respect to a pulmonary vein in the leftatrium of the heart of a patient. The system 10, however, may bealternatively used in any suitable environment and for any suitablereason.

The Elongate Member

The elongate member 12 of the preferred embodiments is a catheter madeof a flexible multi-lumen tube, but may alternatively be a cannula, tubeor any other suitable elongate structure having one or more lumens. Theelongate member 12 preferably has a separate lumen that houses thepositioning mechanism 14, but may alternatively house the positioningmechanism 14 in any other suitable configuration. The elongate member 12preferably houses a single positioning mechanisms 14 (as shown in FIG.1A), but may house more than one positioning mechanisms (as shown inFIG. 2). The elongate member 12 of the preferred embodiments functionsto accommodate pull members, fluids, gases, energy delivery structures,electrical connections, therapy catheters, navigation catheters, pacingcatheters, and/or any other suitable device or element. As shown in FIG.2, the elongate member 12 preferably includes a distal tip assembly 16positioned at a distal portion of the elongate member 12. The distal tipassembly 16 preferably houses an energy delivery structure 18 thatfunctions to deliver energy 20 to tissue, such as tissue of a heart3002. The energy delivery structure 18 preferably includes an ultrasoundtransducer subassembly, but may alternatively include any other suitablesource of ablation energy such as radio frequency (RF) energy,microwaves, photonic energy, and thermal energy. Ablation couldalternatively be achieved using cooled fluids (e.g., cryogenic fluid).

The Positioning Mechanism

As shown in FIGS. 1A and 1B, the positioning mechanism 14 of thepreferred embodiments is coupled to a distal portion of the elongatemember 12. As shown in FIG. 1A, the positioning mechanism 14 ispreferably coupled to the distal tip of the elongate member 12. Thepositioning mechanism 14 is preferably coupled to the distal tip of theelongate member 14 such that fluid (for cooling the energy deliverysystem 18 or for cooling the tissue, for example) is able to flowthrough a lumen in the elongate member 12 and exit out of the elongatemember as necessary. Alternatively, as shown in FIG. 1B, the positioningmechanism 14 is preferably coupled to the side of the elongate member 12near the distal end of the elongate member 12. In some variations, thepositioning member 14 is retractable into and exits from the elongatemember 12 through the distal end or through a notch 22 near the distalend of the elongate member 12. In these variations, the positioningmember 14 preferably is held in or moves to a smaller configuration (byfolding, straightening, etc.) such that it fits within the elongatemember 12. The positioning member, when residing completely inside alumen of the elongate member 12, is preferably held in a generallystraight shape, conforming to confines of the lumen. As the positingmember 14 is advanced outwards, and/or as it exits the notch 22, itpreferably takes on a predetermined shape, for example as shown in FIGS.1B, 5, and 11.

As shown in FIG. 2, the positioning mechanism 14 of the preferredembodiments performs one or more of the following functions: (a)facilitate locating an anatomical structure, (b) anchor the elongatemember 12 with respect to the anatomical structure, and (c) electricallystimulate and/or sense electrical signals from the anatomical structure.Regarding the first function, the positioning mechanism 14 facilitateslocating an anatomical structure by providing an indication of where thepositioning mechanism 14 is with respect to the anatomical structure.The indication is preferably a visual indication (via a medical imagingsystem such as a fluoroscope), but is alternatively or additionally atactile or audible indication. Additionally, the elongate member 12and/or the positioning mechanism 14 may include indicia, such asmarkings indicating distance, that indicate the location of theanatomical structure and/or to indicate the depth of insertion of thesystem 10 where the anatomical structure was located.

Regarding the second function, the positioning mechanism 14 anchors theelongate member 12 with respect to the anatomical structure by couplingto a portion of an anatomical structure (for example a pulmonary vein3000 and/or a left atrium 3002 of a heart) and by providingstabilization of the elongate member 12 when manipulating at least aportion of the elongate member 12 and/or by providing an axis ofrotation to the elongate member 12 as it is rotated. The elongate member12 is preferably manipulated to position the energy delivery structure18 within the left atrium of the heart 3002 (or in any other suitablelocation) and, once positioned there, is preferably manipulated to movethe energy delivery structure 18 along an ablation path and to directthe energy delivery structure 18 towards tissue to provide a partial orcomplete zone of ablation along the ablation path. The ablation pathpreferably has any suitable geometry or geometries to provide aconduction block—isolation and/or block of conduction pathways ofabnormal electrical activity, which typically originate from thepulmonary veins in the left atrium—for treatment of atrial fibrillationin a patient, but may alternatively provide any other suitable therapy.A linear ablation path is preferably created by moving and bending theelongate member 12 in an X, Y, and/or Z direction. A generally circularor elliptical ablation path 30 is preferably created by rotating theelongate member 12 about an axis. The elongate member 12 is preferablyrotated in one of several variations. In a first variation, as shown inFIG. 2, the elongate member is rotated, as shown by arrow 3010, aroundthe two positioning mechanisms 14, the energy delivery structure 18preferably sweeps a generally circular ablation path 30. The twopositioning mechanisms 14 preferably assure that the rotation of theelongate member 12 and therefore the energy delivery structure 18 willoccur in an ablation path 30 outside of the pulmonary veins 3000 and3000′. The ablation path 30 may alternatively encircle a singlepulmonary vein or encircle any other suitable number of pulmonary veins.

In a second variation, as shown in FIG. 3, the elongate member isrotated, as shown by arrow 3012, within the pulmonary vein 3000 suchthat the energy delivery structure 18 preferably sweeps a generallycircular ablation path 30, generally perpendicular to the axis of thepulmonary vein 3000. In an alternative version of this second variation,the elongate member may alternatively be located outside of and adjacentto the pulmonary vein while still generally perpendicular to the axis ofthe pulmonary vein 3000. The elongate member is preferably rotated suchthat the energy delivery structure 18 preferably sweeps a generallycircular ablation path 30 around at least one ostium of a pulmonaryvein. In this version of the second variation, the energy deliverystructure 18 is preferably angled such that it is preferably at an acuteangle with respect to the axis of the elongate member and such that theenergy delivery structure preferably points and delivers energy 20substantially towards the atrial wall and around the pulmonary veinostium. In the second variation, the energy delivery structure 18preferably rotates within the distal tip assembly 16, deliveringablation energy though a window that runs around the circumference ofthe distal tip assembly 16. The window is preferably made of a materialthat is transparent to ultrasound waves such as a poly 4-methyl,1-pentene (PMP) material or may alternatively be an open window.Alternatively, the elongate member 12 and/or distal tip assembly 16 mayrotate, rotating the energy delivery structure within. The positioningmechanism 14 preferably does not rotate along with the elongate member12 and/or the distal tip assembly 16.

In a third variation, as shown in FIG. 4, the positioning mechanism 14is pressed against a portion of a heart chamber (such as the ceilingwall of the left atrium), or in any other suitable location and theelongate member 12 is rotated, as shown by arrow 3014, around the axiscreated by the positioning mechanism 14, the energy delivery structure18 preferably sweeps a generally circular ablation path outside of thepulmonary veins 3000 and 3000′. The ablation path may alternativelyencircle a single pulmonary vein or any other suitable number ofpulmonary veins.

In all variations, the energy delivery structure is preferablypositioned with respect to the tissue at an appropriate angle. Theenergy delivery system is preferably directed towards the target tissueat an angle between 20 and 160 degrees to the tissue, more preferably atan angle between 45 and 135 degrees to the tissue, and most preferablyat an angle of 65 and 115 degrees to the tissue.

Regarding the third function, the positioning mechanism 14 electricallystimulates and/or senses electrical signals from the anatomicalstructure by electrically coupling to the anatomical structure andsending and/or receiving electrical signals to the tissue. Thepositioning mechanism 14 preferably includes an even number ofelectrodes or electrically active portions such that a bipolarelectrical system may be used, wherein each pair of electrodes orelectrically active portions has an opposite polarity. The positioningmechanism 14 may alternatively include a single electrode orelectrically active portion and use a monopolar electrical system, ormay include any other suitable number of electrodes or electricallyactive portions. The positioning mechanism 14 functions to map thetissue by sensing the electrical conduction between the pulmonary veinsand the other parts of the atrial wall on the endocardial side. Thepositioning mechanism 14 functions to pace the tissue and maintain anartificial heart rate (preferably temporarily) by sending electricalpulses to the tissue. The positioning mechanism 14 preferably paces thetissue located in a position distal from the energy delivery structure18 and/or the ablation path 30, such that the energy delivery structure18 and/or the ablation path 30 are between the positioning mechanism 14that is pacing and the beating heart. The positioning mechanism mayalternatively pace tissue in any other suitable location. The recordingand sensing signals received and sent by the positioning mechanism arepreferably compatible with conventional navigation and mapping systemssuch as CARTO XP EP Navigation System (Biosense Webster, Diamond Bar,Calif.), EnSite System (St. Jude Medical, St. Paul, Minn.), and/or anyother suitable mapping, navigation, or visualization system.

As mentioned above, the positioning mechanism 14 of the preferredembodiments performs one or more of the following functions: (a)facilitate locating an anatomical structure, (b) anchor the elongatemember 12 with respect to the anatomical structure, and (c) electricallystimulate and/or sense electrical signals from the anatomical structure.Although the positioning mechanism 14 is preferably one of the severalvariations described below, the positioning mechanism 14 may be anysuitable mechanism to perform one or more of these functions.

First Variation of the Positioning Mechanism

In a first variation, as shown in FIGS. 5, 6A, and 6B, the positioningmechanism 14′ includes a plurality of wires each having a first end 24and a second end 26. The plurality of wires are preferably flexiblewires, but may alternatively be movable in any other suitable fashion.The first end 24 is preferably coupled to the distal tip of the elongatemember 12, but may alternatively be attached in any other suitablelocation (shown in FIG. 4). The second end 26 preferably extends fromthe distal tip of the elongate member and is positioned in a fullyextended position, as shown in FIG. 5. The second end 26 preferablydeflects due to contact with a surface, as shown in FIGS. 6A and 6B. Thesecond end 26 is preferably biased towards the fully extended position,but may alternatively be biased towards any other suitable position. Thefirst end 24 is preferably slidably coupled to the elongate member 12such that it is partially or fully retractable into the elongate member12. For example, the plurality of wires may be pushed or pulled throughthe distal tip of the elongate member 12 by a wire that extends throughthe elongate member 12. The plurality of wires may be pulled backthrough the distal tip of the elongate member 12 in order to return thewires to the fully extended position, as shown in FIG. 5. The pluralityof wires may alternatively be fixed to the distal tip of the elongatemember 12 or coupled to the elongate member 12 in any other suitablefashion. The wires are preferably made from a conductive material and/ora material with shape memory such as nickel/titanium or a shape memorypolymer. The material is preferably flexible so as not to cause injuryto the tissue of the heart where the positioning mechanism 14′ mightcontact and move against it. At least a portion of each wire ispreferably made from a fluoro-opaque material, such as platinum or gold,such that it may be seen while positioned inside the internal structuresof a patient through the use of a fluoroscope. The fluoro-opaque portion28 is preferably located at the second end 26 of a wire, but mayalternatively be located in any suitable position such that it may beseen while positioned inside the internal structures of a patientthrough the use of a fluoroscope. The fluoro-opaque portion ispreferably flush with the wire, but may alternatively have a round orany other suitable shape such that it will not damage the tissue.Additionally, the plurality of wires preferably includes at least oneelectrically active portion and/or at least one insulated portion (e.g.an insulating coating on a portion of each wire). The electricallyactive portion is preferably located at the second end 26 of a wire, butmay alternatively be located in any suitable position, such as thecenter portion, such that it conies in contact with tissue.

The plurality of wires preferably has any suitable geometry such thatpositioning mechanism 14′ may perform any combination of functionsdescribed. Additionally, the plurality of wires preferably have a lengthand/or geometry such that when they deflect, they do not cover, block,or lay in front of the energy delivery structure 18, or any portionthereof Therefore, they preferably do not block any portion of theenergy delivered by the energy delivery structure 18 and cause a“shadow” effect. In a first version, as shown in FIG. 5, the wires aresubstantially straight. In a second version, as shown in FIG. 8A, thewires are curved or bent such that they are biased away from theelongate member 12. In a third version, as shown in FIG. 8B, theplurality of wires includes six wires circumferentially disposed aroundthe elongate member 12. The plurality of wires preferably includes aneven number of wires, but may alternatively include a single wire or anyother suitable number of wires. In a fourth version, as shown in FIG.8C, the plurality of wires includes multiple tiers or layers of wires.Each tier or layer may include any suitable number of wires and eachtier or level may include a different number of wires from any othertier or level.

As shown in FIGS. 6A and 6B, the plurality of wires function tofacilitate locating an anatomical structure by flexing as they come incontact with the anatomical structure. For example, the wires willremain fully extended from the elongate member 12 when they areunobstructed in the left atrium of the heart 3002, as shown in FIG. 4.As the system 10 is moved within the left atrium of the heart 3002 andbegins to contact the ostium (opening) of a pulmonary vein 3000, theplurality of wires will begin to deflect partially, as shown in FIG. 6A.As the system 10 is moved into the pulmonary vein 3000, the wires willdeflect more dramatically as shown in FIG. 6B. As the system is moveddeeper into the pulmonary vein, the wires will not deflect as much, ifat all, and an operator of the system 10 will be able to determine whenthe positioning mechanism 14 of the system 10 is correctly locatedwithin the pulmonary vein.

Furthermore, as shown in FIG. 7, the angle 3004 at which the system 10enters the pulmonary vein 3000 with respect to the longitudinal axis ofthe pulmonary vein 3000 is determined. For example, if the system 10 isentering the pulmonary vein 3000 at angle 3004, a wire to the left ofthe elongate member 12 will deflect to an angle 3006 with respect to theelongate member 12 while a wire to the right of the elongate member 12will deflect to an angle 3008 with respect to the elongate member 12.Therefore, the angle 3004 at which the system 10 is entering thepulmonary vein 3000 is preferably determined from the size of angles3006 and 3008. These angles 3006 and 3008 are preferably detectedvisually under fluoroscopic guidance by the operator of the system 10,but may alternatively be detected and processed by a processor in orderto determine angle 3004. Upon the detection of the angle 3004, anoperator of the system 10 is alerted of an off-center entry, theoperator adjusts and centers the system 10 and/or is instructed on howto do so. The system 10 may alternatively be adjusted automaticallythrough a motor drive system or any other suitable system. The ablationpath 30 is preferably altered such that energy delivery structure willbe located substantially the same distance from each point of tissuealong the ablation path 3 and/or the energy delivery structure ispreferably adjusted to accommodate an off-center entry. The energydelivery structure is preferably adjusted by changing the power and/orfrequency, bandwidth, and amplitude of the sound wave propagated intothe tissue along certain portions of an ablation path 30. Due to anoff-center entry, the energy delivery structure will be closer to sometissue along the ablation path 30 and further away from other tissue. Inone example, the energy delivery structure is adjusted to use less powerfor the portions of the tissue that are closer to the energy deliverystructure.

The plurality of wires function to anchor the elongate member 12 withrespect to the anatomical structure, preferably a pulmonary vein 3000,by coupling to the anatomical structure. The outward biasing force ofthe plurality of wires against the interior wall of the pulmonary veinwill preferably hold the positioning mechanism 14′ within the pulmonaryvein due to friction. Alternatively, the tips of the plurality of wiresmay function as barbs such that the plurality of wires are preferablyadvanced into the pulmonary vein, but the tips of the wires will preventthe positioning mechanism 14 from being pulled out of the pulmonaryvein. In this version, the wires may be manually retracted uponcompletion of the procedure to allow for the removal of the positioningmechanism 14′. The positioning mechanism may alternatively function toanchor the elongate member 12 with respect to the anatomical structurein any other suitable fashion.

Second Variation of the Positioning Mechanism

In a second variation, as shown in FIGS. 9A and 9B, the positioningmechanism 14″ includes a plurality of wires, a first end cap 32, asecond end cap 34, and a pull member 36. The plurality of wires arecircumferentially disposed around the elongate member 12. The pluralityof wires preferably includes an even number of wires such as two, four,six, eight, or more, but may alternatively include a single wire or anyother suitable number of wires. The first end cap 32 is preferablycoupled to the distal tip of the elongate member 12, but mayalternatively be attached in any other suitable location, as shown inFIG. 4. The second end cap 34 preferably extends from the distal tip ofthe elongate member 12 along the longitudinal axis of the elongatemember 12 and transitions between a fully extended position, as shown inFIG. 9A, and a retracted position, as shown in FIG. 9B. When the secondend cap 34 is in the fully extended position, the wires are preferablysubstantially straight. When the second end cap 34 is in the retractedposition, the wires preferably flex and bend at one location along thewire to form a basket or cage-like structure. The second end cap 34preferably transitions between a fully extended position and a retractedposition by pulling the pull member 36. The pull member 36 is preferablycoupled to the second end cap 34 and runs through the first end cap 32such that the first end cap 32 is slidably coupled to the pull member36. Preferably, the pull member 36 is attached to the second end cap 34with an adhesive band, but may alternatively be coupled to the secondend cap 34 with any other suitable chemical and/or mechanical connectionsuch as adhesive, welding, pins and/or screws. The pull member ispreferably disposed within a lumen of the first end cap and the elongatemember 12, but may alternatively be held in any suitable location. Thepull member preferably terminates at a slider in a proximal housing (notshown) that preferably includes various actuating mechanisms totransition the second end cap from the fully extended position to theretracted position. The second end cap preferably returns to the fullyextended position by the spring force of the plurality of wires (theyare preferably biased towards the substantially straight position), butmay alternatively return to the fully extended position in any othersuitable fashion.

The wires may alternatively flex or bend in multiple locations and eachwire may bend in a different location. The wires are preferably biasedtowards the substantially straight position, but may alternatively bebiased towards the bent position or any other suitable position. Thewires are preferably made from a conductive material and/or a materialwith shape memory such as nickel/titanium alloys or a shape memorypolymer, but may alternatively be made from any suitable material suchas plastic. The material is preferably flexible so as not to causeinjury to the tissue of the heart where the positioning mechanism 14might contact and move against it. At least a portion of each wire ispreferably made from a fluoro-opaque material (also referred to hereinusing the term “radiopaque”), such as platinum or gold, such that it maybe seen while positioned inside the internal structures of a patientthrough the use of a fluoroscope. The fluoro-opaque portion ispreferably located in any suitable position such that it may be seenwhile positioned inside the internal structures of a patient through theuse of a fluoroscope. The fluoro-opaque portion is preferably flush withthe wire, but may alternatively have a round or any other suitable shapesuch that it will not damage the tissue. Additionally, the plurality ofwires preferably includes at least one electrically active portionand/or at least one insulated portion (e.g. an insulating coating on aportion of each wire). The electrically active portion is preferablylocated towards the center portion of each wire, but may alternativelybe located in any suitable position such that it comes in contact withtissue.

The positioning mechanism 14″ functions to facilitate locating ananatomical structure by the plurality of wires flexing as they come incontact with the anatomical structure. For example, when the wires areflexed or bent as shown in FIG. 9B, and as the system 10 is moved withinthe left atrium of the heart 3002 and begins to contact the ostium(opening) of a pulmonary vein 3000, the plurality of wires will begin todeflect inward or away from the adjacent wires due to contact with atissue surface. As the system is moved deeper into the pulmonary vein,the wires will not deflect as much if at all, and an operator of thesystem 10 will be able to determine when the positioning mechanism 14″of the system 10 is correctly located within the pulmonary vein.

The plurality of wires of the positioning mechanism 14″ function toanchor the elongate member 12 with respect to the anatomical structure,preferably a pulmonary vein 3000, by coupling to the anatomicalstructure. Preferably, the outward force of the plurality of wires inthe flexed or bent position, as shown in FIG. 9B, against the interiorwall of the pulmonary vein will hold the positioning mechanism 14″within the pulmonary vein due to friction. In this version, the secondend cap 34 will be returned to the fully extended position uponcompletion of the procedure, straightening the plurality of wires, toallow for the removal of the positioning mechanism 14″. The positioningmechanism 14″ may alternatively function to anchor the elongate member12 with respect to the anatomical structure in any other suitablefashion.

Third, Fourth, and Fifth Variation Positioning Mechanism

In a third variation, as shown in FIGS. 10A and 10B, the positioningmechanism is a combination of the first and second variations of thepositioning mechanisms 14′ and 14″. In this variation, the positioningmechanism preferably includes two pluralities of wires. The firstplurality of wires has a first end 24 and a second end 26 as describedabove, and the second plurality of wires has a first end cap 32, asecond end cap 34, and a pull member 36 also as described above. Whenthe second end cap 34 is in the retracted position, as shown in FIG.10B, the second plurality of wires preferably flex and bend in onelocation to form a basket or cage-like structure. The first plurality ofwires deflect due to contact with a surface and will preferably deflectdown and in between the second plurality of wires such that they willnot obstruct the function of the second plurality of wires.

In a fourth variation, as shown in FIG. 11, the positioning mechanism14′ is a coil. The coil is preferably made from a conductive materialand/or a material with shape memory such as nickel/titanium alloys or ashape memory polymer. The material is preferably flexible so as not tocause injury to the tissue of the heart where the positioning mechanism14 might contact and move against it. At least a portion of the coil ispreferably made from a fluoro-opaque material, such as platinum or gold,such that it may be seen while positioned inside the internal structuresof a patient through the use of a fluoroscope. The fluoro-opaque portionis preferably located in any suitable position such that it may be seenwhile positioned inside the internal structures of a patient through theuse of a fluoroscope. The fluoro-opaque portion is preferably flush withthe wire, but may alternatively have a round or any other suitable shapesuch that it will not damage the tissue. Additionally, the coilpreferably includes at least one electrically active portion and/or atleast one insulated portion (e.g. an insulating coating on a portion ofeach wire). The electrically active portion is preferably located in anysuitable position such that it comes in contact with tissue.

The positioning mechanism 14″′ functions to facilitate locating ananatomical structure by the coil flexing as it comes in contact with theanatomical structure. For example, as the system 10 is moved within theleft atrium of the heart 3002 and begins to contact the wall of theatrium or the ostium (opening) of a pulmonary vein 3000, the coil willbegin to deflect. As the system is moved deeper into the pulmonary vein,the wires will not deflect as much if at all, and an operator of thesystem 10 will be able to determine when the positioning mechanism 14″′of the system 10 is correctly located within the pulmonary vein.

The coil of the positioning mechanism 14″′ functions to anchor theelongate member 12 with respect to the anatomical structure, preferablya pulmonary vein 3000, by coupling to the anatomical structure.Preferably, the outward force of the coil against the interior wall ofthe pulmonary vein will hold the positioning mechanism 14″′ within thepulmonary vein due to friction. The positioning mechanism 14″′ mayalternatively function to anchor the elongate member 12 with respect tothe anatomical structure in any other suitable fashion.

In a fifth variation, as shown in FIG. 12, the positioning mechanismincludes at least one distal wire 38 and at least one proximal wire 40,each wrapped around at least a portion of the elongate member 12. Thewires are preferably made from a conductive material and/or a materialwith shape memory such as nickel/titanium alloys or a shape memorypolymer. The material is preferably flexible so as not to cause injuryto the tissue of the heart where the wires might contact and moveagainst it. At least a portion of each of the wires is preferably madefrom a fluoro-opaque material, such as platinum or gold, such that itmay be seen while positioned inside the internal structures of a patientthrough the use of a fluoroscope. The fluoro-opaque portion ispreferably located in any suitable position such that it may be seenwhile positioned inside the internal structures of a patient through theuse of a fluoroscope. The fluoro-opaque portion is preferably flush withthe wire, but may alternatively have a round or any other suitable shapesuch that it will not damage the tissue. Additionally, each of the wirespreferably includes at least one electrically active portion 42 and/orat least one insulated portion (e.g. an insulating coating on a portionof each wire). The wires each preferably include an even number ofelectrically active portions 42 such that a bipolar electrical systemmay be used, wherein each pair of electrodes or electrically activeportions has an opposite polarity. For clarity, only a singleelectrically active portion 42 per wire has been shown in FIG. 12. Thewires may alternatively include a single electrode or electricallyactive portion and use a monopolar electrical system, or may include anyother suitable number of electrodes or electrically active portions. Theelectrically active portion 42 is preferably located in any suitableposition such that it comes in contact with tissue. The distal wire 38is preferably located distally from the energy delivery structure 18,and the proximal wire is preferably located proximally from the energydelivery structure. The wires are preferably each coupled to theelongate member 12 at one end of the wire and then the other end ispreferably wrapped around at least a portion of the elongate member 12such that the other ends unwind towards the tissue once the distal tipassembly 16 is placed within the pulmonary vein 3000 or any othersuitable structure. The wires preferably unwind such that theelectrically active portion 42 of each wire is in contact with thetissue. The wires are preferably wrapped around the elongate member suchthat as the elongate member 12 and/or distal tip assembly are rotated(as shown by arrow R in FIG. 12), the electrically active portions 42 ofthe wires sweep along the tissue. The wires are further preferablywrapped around at least a portion of the elongate member such that theyare biased away from one another. For example, the distal wire 38 may bewrapped such that the end is biased towards the distal end of thecatheter. This will encourage the wires to not block the energy deliverystructure and to not contact one another. There is preferably at leastone distal wire and at least one proximal wire such that, as the energydelivery structure 18 delivers energy to the tissue to form an ablationpath and/or conduction block, there will be at least one wire distal tothe conduction block and at least one wire proximal to the ablation pathand/or conduction block.

Although omitted for conciseness, the preferred embodiments includeevery combination and permutation of the various elongate members 12 andpositioning mechanism 14.

While the above is a complete description of the preferred embodimentsof the invention, various alternatives, modifications, and equivalentsmay be used. Therefore, the above description should not be taken aslimiting in scope of the invention which is defined by the appendedclaims.

What is claimed is:
 1. A method of ablating a target tissue, said methodcomprising: providing an elongate shaft having a proximal end and adistal end; positioning the distal end of the elongate shaft adjacentthe target tissue; delivering energy to the target tissue with an energydelivery element housed within an energy delivery structure disposednear the distal end of the shaft, without contacting the target tissuewith the energy delivery structure and the energy delivery elementdisposed therein, thereby creating a zone of ablation in the targettissue; and moving the energy delivery structure along an ablation pathwhile delivering energy with the energy delivery element, withoutcontacting the zone of ablation with the energy delivery structure andthe energy delivery element disposed therein.
 2. A device for ablating atarget tissue, said device comprising: an elongate shaft having aproximal end and a distal end; an energy delivery structure disposednear the distal end of the elongate shaft; and an energy deliveryelement housed within the energy delivery structure, the energy deliveryelement configured to deliver energy to the target tissue withoutcontacting the target tissue, thereby creating a zone of ablation in thetarget tissue, and wherein the energy delivery structure is configuredto move along an ablation path while the energy delivery elementdelivers energy, without contacting the zone of ablation with the energydelivery structure and the energy delivery element disposed therein.